When applying indicia to both sides of a sheet of paper, it is desirable to maintain a specified registration between indicia on a front side of the sheet and indicia of the back side of the sheet. The registration noted above assumes a particular dimensionality of the sheet. Known systems and methods for applying indicia, such as xerography, dry ink printing, aqueous ink printing, and lithography, to two sides of a sheet of paper involve operations on the first/top side of the sheet, such as applying heat and pressure, or adding liquid, which can change the dimensions, for example length, of the sheet, for example by changing the moisture content of the sheet or stretching the sheet. When the application of indicia to the top sheet changes the dimensions of the sheet, the assumed dimensionality is no longer accurate and subsequently, the indicia applied to the back side can be out of registration with indicia on the front side.
For example, a xerographic machine passes a sheet through a fuser to fix indicia on a front side of a sheet. The fuser applies heat and pressure which can drive moisture out of the sheet, shrinking the sheet and changing the length of the sheet. Thus, the image magnification for the front side is not appropriate for image magnification for a back side of the sheet, and mis-registration occurs between print on the front and back sides of the sheet. It is known to use a manual measurement procedure to measure mis-registration on a sheet of paper. However, the procedure requires an operator to manually measure a test pattern on both sides of a printed sheet, which is time consuming and prone to operator error.
Many factors contribute to the dimensional change, for example an amount of paper shrinkage through the fuser of a xerographic machine. These factors include: paper type, environmental conditions, and machine settings/conditions. In addition to the time and error problems noted above, the manual measurement described above is only a snapshot in time and needs to be performed again whenever there is a change in any of these factors.